The Global Positioning System (GPS) has long been employed by the military to accurately determine the position of any given person or object around the globe. In the civilian arena, GPS-based applications have also proliferated. GPS positioning has been employed for purposes as diverse as navigation, farming, telecommunication, location-based marketing and advertising, etc.
Electronic devices, and more particularly portable electronic devices, are ubiquitous these days. For example, a typical consumer may carry at times an electronic key fob for opening/closing automobile doors, a cellular phone for communication, a portable music/video player for entertainment, etc.
Since these devices all contain tightly packed, highly sensitive electronic circuitry, electrostatic discharge (ESD) protection is an important consideration. Generally speaking, electrostatic discharge refers to static electricity discharge that can occur when the electronic device is exposed to a nearby object having a higher electrical potential (i.e., the ESD source). In the typical case, a spark between the object having the higher electrical potential and the electronic device may occur when so exposed. The discharge current path (of which the spark is a part) may traverse one or more sensitive circuits in the electronic device, causing a temporary or permanent malfunction.
Given the potential damage that ESD poses to modern electronic devices, many approaches have been proposed and implemented to protect electronic devices against ESD-related damage. A common approach is to provide certain circuits or components with ESD protection circuitry, such as discharge diodes, etc. Another common approach is to physically shield a portion or all of the vulnerable components with an ESD shield. Other approaches have also been proposed and/or implemented.
Generally speaking, an ESD shield is a conductive shield that presents to the ESD source a lower resistance path to ground. The discharge current that emanates from the ESD source is then diverted onto the ESD shield, thereby preventing the discharge current from causing damage to the sensitive electronic components.
In a typical device, there is typically a conductive or insulative housing or cover that acts as an environmental enclosure and also provides a pleasing cosmetic appearance. For example, a typical cellular phone may be encased in a plastic or aluminum housing that provides a mounting framework for the electronic components therein as well as protects the electronic components from environmental damage.
ESD current typically cannot penetrate the conductive or insulative housing material. Instead, ESD current penetrates the electronic device through joints or interfaces where the housing parts are assembled together. In an example cellular phone, there may be two half shells that form the housing. The joint between these two shells are often vulnerable to ESD current penetration and is often the focus for ESD protection. If one of the shells has other openings, such as an opening to accommodate a battery or a LCD (Liquid Crystal Display) sub-assembly, the opening edges are also vulnerable to ESD current penetration.
If there are multiple joints and openings in a given housing, one approach to ESD protection is to provide an ESD shield at any location where ESD current penetration may occur. However, this approach also increases the mass and thickness of the resultant electronic device. Given the trend toward device miniaturization and the need to pack more functionality and capability into each device (which necessitates an ever-increasing number of circuits packed into an ever-shrinking form factor), engineers are constantly looking for ways to maintain or improve ESD protection while eliminating bulk and materials from the finished product. Further, to maximize market appeal, the finished product has to be aesthetically pleasing. ESD protection schemes must therefore also take aesthetic into consideration. Improving ESD protection while minimizing bulk and maintaining a pleasing aesthetic appearance is a subject of the present invention.